ElemenetType.CONSTRUCTOR 构造器声明
ElemenetType.FIELD 域声明(包括 enum 实例) 
ElemenetType.LOCAL_VARIABLE 局部变量声明 
ElemenetType.METHOD 方法声明 
ElemenetType.PACKAGE 包声明 
ElemenetType.PARAMETER 参数声明 
ElemenetType.TYPE 类，接口(包括注解类型)或enum声明

RetentionPolicy.SOURCE 注解将被编译器丢弃 
RetentionPolicy.CLASS 注解在class文件中可用，但会被VM丢弃 
RetentionPolicy.RUNTIME VM将在运行期也保留注释，因此可以通过反射机制读取注解的信息

package com.test.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;


public class MyAnnotation {
  
  /**
   * 注解类
   * @author T4980D
   *
   */
  @Retention(RetentionPolicy.RUNTIME) 
  @Target(ElementType.TYPE) 
  public @interface MyClassAnnotation { 
    String uri(); 
    String desc(); 
  } 
  
  /** 
   * 构造方法注解 
   * @author T4980D 
   * 
   */ 
  @Retention(RetentionPolicy.RUNTIME)   
  @Target(ElementType.CONSTRUCTOR)  
  public @interface MyConstructorAnnotation { 
   
    String uri(); 
    String desc(); 
  } 
  
  /** 
   * 我的方法注解 
   * @author Owner 
   * 
   */ 
  @Retention(RetentionPolicy.RUNTIME)   
  @Target(ElementType.METHOD) 
  public @interface MyMethodAnnotation { 
   
    String uri(); 
    String desc(); 
  } 
  
  /** 
   * 字段注解定义 
   * @author Owner 
   * 
   */ 
  @Retention(RetentionPolicy.RUNTIME)   
  @Target(ElementType.FIELD)  
  public @interface MyFieldAnnotation { 
   
    String uri(); 
    String desc(); 
  } 
  /**
   * 
   * 可以同时应用到类上和方法上
   * @author T4980D
   *
   */
  @Target({ElementType.TYPE, ElementType.METHOD})
  @Retention(RetentionPolicy.RUNTIME)
  public @interface Yts {
    // 定义枚举
    public enum YtsType {
      util, entity, service, model
    }

    // 设置默认值
    public YtsType classType() default YtsType.util;
    
    // 数组
    int[] arr() default {3, 7, 5};

    String color() default "blue";
  }
    
}

package com.test.annotation;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;

import com.test.annotation.MyAnnotation.MyClassAnnotation;
import com.test.annotation.MyAnnotation.MyConstructorAnnotation;
import com.test.annotation.MyAnnotation.MyFieldAnnotation;
import com.test.annotation.MyAnnotation.MyMethodAnnotation;
import com.test.annotation.MyAnnotation.Yts;
import com.test.annotation.MyAnnotation.Yts.YtsType;

@MyClassAnnotation(desc = "The class", uri = "com.test.annotation.Test")
@Yts(classType =YtsType.util)
public class TestAnnotation {
  @MyFieldAnnotation(desc = "The class field", uri = "com.test.annotation.Test#id")
  private String id;

  @MyConstructorAnnotation(desc = "The class constructor", uri = "com.test.annotation.Test#MySample")
  public TestAnnotation() {
  }

  public String getId() {
    return id;
  }

  @MyMethodAnnotation(desc = "The class method", uri = "com.test.annotation.Test#setId")
  public void setId(String id) {
    System.out.println(" method info: "+id);
    this.id = id;
  }
  
  @MyMethodAnnotation(desc = "The class method sayHello", uri = "com.test.annotation.Test#sayHello")
  @Yts 
  public void sayHello(String name){ 
    if(name == null || name.equals("")){ 
      System.out.println("hello world!"); 
    }else{ 
      System.out.println(name + "\t:say hello world!"); 
    } 
  } 
  public static void main(String[] args) throws Exception {

    Class<TestAnnotation> clazz = TestAnnotation.class;
    // 得到类注解
    MyClassAnnotation myClassAnnotation = clazz.getAnnotation(MyClassAnnotation.class);
    System.out.println(myClassAnnotation.desc() + " "+ myClassAnnotation.uri());

    // 得到构造方法注解
    Constructor<TestAnnotation> cons = clazz.getConstructor(new Class[]{});
    MyConstructorAnnotation myConstructorAnnotation = cons.getAnnotation(MyConstructorAnnotation.class);
    System.out.println(myConstructorAnnotation.desc() + " "+ myConstructorAnnotation.uri());

    // 获取方法注解
    Method method = clazz.getMethod("setId", new Class[]{int.class});
    MyMethodAnnotation myMethodAnnotation = method.getAnnotation(MyMethodAnnotation.class);
    System.out.println(myMethodAnnotation.desc() + " "+ myMethodAnnotation.uri());
    // 获取字段注解
    Field field = clazz.getDeclaredField("id");
    MyFieldAnnotation myFieldAnnotation = field.getAnnotation(MyFieldAnnotation.class);
    System.out.println(myFieldAnnotation.desc() + " "+ myFieldAnnotation.uri());
  }

}

package com.test.annotation;

import java.lang.reflect.Method;
import java.util.Arrays;

import com.test.annotation.MyAnnotation.MyClassAnnotation;
import com.test.annotation.MyAnnotation.MyMethodAnnotation;
import com.test.annotation.MyAnnotation.Yts;
import com.test.annotation.MyAnnotation.Yts.YtsType;

public class ParseAnnotation {

  /**
   * 解析方法注解
   * @param <T>
   * @param clazz
   */
  public static <T> void parseMethod(Class<T> clazz) {
    try {
      T obj = clazz.newInstance();
      for (Method method : clazz.getDeclaredMethods()) {
        MyMethodAnnotation methodAnnotation = method.getAnnotation(MyMethodAnnotation.class);
        if (methodAnnotation!=null) {
          //通过反射调用带有此注解的方法
          method.invoke(obj, methodAnnotation.uri());
        }
        Yts yts = (Yts) method.getAnnotation(Yts.class);
        if (yts != null) {
          if (YtsType.util.equals(yts.classType())) {
            System.out.println("this is a util method");
          } else {
            System.out.println("this is a other method");
          }
          System.out.println(Arrays.toString(yts.arr())); //打印数组
          System.out.println(yts.color()); //输出颜色
        }
        System.out.println("\t\t-----------------------");
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

  /**
   * 解析类注解
   * @param <T>
   * @param clazz
   */
  public static <T> void parseType(Class<T> clazz) {
    try {
      Yts yts = (Yts) clazz.getAnnotation(Yts.class);
      if (yts != null) {
        if (YtsType.util.equals(yts.classType())) {
          System.out.println("this is a util class");
        } else {
          System.out.println("this is a other class");
        }
      }
      MyClassAnnotation classAnnotation = (MyClassAnnotation) clazz.getAnnotation(MyClassAnnotation.class);
      if (classAnnotation != null) {
        System.err.println(" class info: "+classAnnotation.uri());
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
  
  public static void main(String[] args) {
    parseMethod(TestAnnotation.class);
    parseType(TestAnnotation.class);
  }

}

@Retention(RetentionPolicy.RUNTIME)//代表Permission注解保留在的阶段 
@Target(ElementType.METHOD)//标注在方法上面 
public @interface Permission { 
 
  /** 模块 */ 
  String module(); 
  /** 权限值 */ 
  String privilege(); 
   
} 

@Permission(module="department",privilege="view") 
public String departmentlistUI(){ 

} 

String actionName=invocation.getProxy().getActionName(); 
String methodName=invocation.getProxy().getMethod(); 
     
System.out.println("拦截到：action的名字："+actionName+"方法名："+methodName); 

private boolean validate(ActionInvocation invocation) throws SecurityException, NoSuchMethodException { 
     
    String methodName=invocation.getProxy().getMethod(); 
     
    Method currentMethod = invocation.getAction().getClass().getMethod(methodName); 
     
    if(currentMethod != null && currentMethod.isAnnotationPresent(Permission.class)){ 
      //得到方法上的注解 
      Permission permission = currentMethod.getAnnotation(Permission.class); 
      //该方法上的所需要的权限 
      SystemPrivilege methodPrivilege = new SystemPrivilege(new SystemPrivilegePK(permission.module(), permission.privilege())); 
      //得到当前登录的用户 
      Employee e = (Employee) ActionContext.getContext().getSession().get("loginUser"); 
      //遍历当前用户下的所有的权限组 
      for(PrivilegeGroup group : e.getGroups()){ 
        //如果该权限组下包含，要访问该方法所需要的权限，就放行 
        if(group.getPrivileges().contains(methodPrivilege)){ 
          return true; 
        } 
         
      } 
      //说明遍历的该用户所有的权限组，没有发现该权限，说明没有该权限 
      return false; 
        
    } 
    //没有标注注解，表示谁都可以调用该方法 
    return true; 
  }